Many types of security systems presently in operation, including the one described in Levinson and Caldicott, U.S. Pat. No. 4,611,198, provide a means for alerting a central station that an emergency is occurring. In the Levinson and Caldicott patents the system has a security zone that is made up of a number of security nodes, each having a relay station for receiving signals and transmitting them to a central station. The activation of a personal security transmitter sends a signal to the central station via the relay station.
Unfortunately, the signal from a personal security transmitter may be picked up not only by the closest relay station but also by adjacent relay stations. The signals from all of these stations reach the central station and it is then difficult to tell which of the relay stations is closest to the emergency. Valuable time can be lost in trying to find the emergency, particularly when the emergency involves a situation in which the person activating the alarm is incapacitated shortly after activation of the alarm.
There is a need for a security system that can sort through a number of alarm signals transmitted from more than one zone, and determine promptly to which zone emergency assistance should be sent.
It is therefore an object of the present invention to provide an improved security and communication system that allows for the accurate determination of the location of the activator of an alarm.
Other objects and advantages of the present invention will become apparent as the description proceeds.